diff --git a/Source/Modules/InputHandler_Core.swift b/Source/Modules/InputHandler_Core.swift
index af1cc0b8..f096f17a 100644
--- a/Source/Modules/InputHandler_Core.swift
+++ b/Source/Modules/InputHandler_Core.swift
@@ -61,6 +61,7 @@ public protocol InputHandlerDelegate {
   var state: IMEStateProtocol { get set }
   var clientBundleIdentifier: String { get }
   func callError(_ logMessage: String)
+  func updateVerticalTypingStatus()
   func switchState(_ newState: IMEStateProtocol)
   func candidateController() -> CtlCandidateProtocol?
   func candidateSelectionCalledByInputHandler(at index: Int)